New cyclopentenyl (CPE)-carbocyclic nucleosides inspired by the structure of the fermentation product neplanocin A were synthesized and evaluated for antitumor and antiviral activity. 8-Aza-neplanocin A was found to possess significant antiviral activity against human cytomegalovirus (HCMV)-infection. Two carba-psicofuranose precursors required to access novel cyclopentenyl-C-nucleosides were synthesized.